1. Field of the Invention
The present invention relates to a movable rack system to be installed in a narrowly limited space, for example in a warehouse, namely a movable rack system having a plurality of movable racks that can travel freely back and forth on a travel path by means of wheels. Especially it relates to a movable rack system allowing movable racks to travel freely back and forth without being guided by a rail (in a trackless manner).
2. Description of the Related Art
An example of a conventional movable rack system allowing free reciprocating trackless traveling is disclosed in Patent Literature 1.
More particularly, such a system is disclosed, where a plurality of movable racks that can travel freely back and forth on a travel path (in a trackless manner) by means of wheels are disposed between stationary racks, so that a corridor is opened up between the adjacent stationary rack and a movable rack or between adjacent movable racks by the travels of the movable racks, and goods are delivered to/from the stationary rack or the movable rack, which face the corridor. therethrough
Wheels located at both sides of each movable rack in the left and right direction, which is perpendicular to the extending direction of the travel path, are respectively provided with driving motors to constitute driven travel wheels. Further, pulse encoders are disposed at both the sides and a movable rack controller is also provided to control the drive rotation amount of both the driving motors, respectively.
The movable rack controller counts pulses of the respective pulse encoders to determine the travel distances of the respective driven travel wheels at both the sides, determines the deviation and the change rates of the travel distances, and controls the speeds of the respective driving motors (the drive rotation amount) so as to eliminate the deviation of the predictive travel distances predicted from the deviation and the change rates of the travel distances, so that the attitude of the movable rack is maintained without being skewed during the travel (execution of attitude control).
In this manner, the attitude control is executed by the movable rack controller during the reciprocating travels of the movable rack along the travel path, so that skewing of the movable rack during the travel and narrowing of the corridor to disturb the goods delivery can be prevented even in the trackless condition.
Further, a sheet rail member to be detected is laid on the floor surface along the travel path, and a widthwise shift detecting means is equipped to detect a deviation in the left and right direction (a widthwise shift) of the movable rack by detecting the member. When the detected widthwise shift exceeds a pre-determined value, the movable rack controller controls the speeds (drive rotation amount) of the respective driving motors to eliminate the widthwise shift, so that the movable rack does not deviate in the left and right direction (execution of widthwise shift control).    [Patent Literature 1] JP3804462B